This invention relates to propellants and more particularly concerns vastly improved modifiers or combustion catalysts for smokeless, high-energy propellants containing nitramines, although not limited thereto.
A most desirable characteristic of any propellant system is reliability of performance which is dependent upon many factors, one being its ballistic properties. A major factor in promoting dependable ballistic properties is the successful development of propellants with burning rates which are invariant or nearly invariant to changes in pressure and temperature. In this respect, desirable isotherms are of negative or zero slope (mesa and plateau burning) and are only slightly temperature dependent (low temperature coefficients, .pi.P, %/.degree.F).
In the pase, almost exclusively, metalo-organo and inorganic compounds of lead with chelated derivatives were found to be most effective as ballistic modifiers for double-base propellants. Because of current demands for higher energy propellants, greater emphasis is now being placed on the development of combustion catalysts which are effective at high energy levels. Propellants of this type are vital in close support weapon systems where performance reliability and smokelessness are prime requirements, and include, among others, the nitramine (RDX, HMX) nitrocellulose base propellants of high volumetric impulse of the following types: extruded smokeless nitramine double-base propellants; plastisol (cast type) smokeless nitramine double-base propellants, and the like.
Prior efforts to ballistically modify these propellants with modifiers employed in the straight double-base systems (metalo organic and inorganic salts) met with limited success and resulted in minimum acceptable "straight line" ballistics for these systems. Even though the effectiveness of modification was minimal for these propellant types, most efficient ballistic modification was obtained with solvent extruded type systems containing metalo organic and inorganic salts. Plastisol (cast type) systems which employ Fluid Ball Powder, to be hereinafter described, as the polymeric binder, resisted nearly all attempts at ballistic modification. For this system, lead stannate hydrate was found to be the most effective combustion catalyst. Cross-linked plastisol (cast type) propellants resisted all ballistic modification with currently known combustion catalysts.
Fluid Ball Powders, trademark products of Olin Mathieson Chemical Corporation, used in the formulation of many of my inventive products, having an average particle size of aobut 7 microns, have the following compositions:
TABLE I ______________________________________ Composition of Fluid Ball Powder Type B Type C ______________________________________ Nitrocellulose, 12.6%N, % 90.0 74.0 Nitroglycerin, % 8.0 24.0 2-Nitrodiphenylamine, % 2.0 2.0 Dioctylphthalate, added, % 0.2 0.1 Carbon black, added % 0.01 to 0.3 -- ______________________________________
It would be most advantageous if new combustion catalysts for crosslinked and uncross-linked high energy smokeless nitramine double-base propellants could be developed which would impart improved and unique ballistic quality of invariance of burning rate to changing temperature and pressure conditions thereto.